Encoding systems with related video encoders and audio encoders are used for various applications, e.g. for TV broadcasting purposes. In this case the video encoders can have variable encoding delay of up to 1.5 sec, depending for example upon the selected bit rate. Therefore, the audio and video delay should be aligned before multiplexing and transmitting the audio and video streams, because of buffer limitations in the decoders of consumer products.
A basic mechanism for controlling delay within the audio encoder by help of a time stamping mechanism can be found in the European patent application 99250009. In a multi-channel audio encoder board input time stamps are generated which become linked at least in one input processing stage with frames of audio data to be encoded, wherein the input time stamps or time stamps derived from the input time stamps remain linked with the correspondingly processed frame data in the different processing stages in the processing, but are at least in the last processing stage replaced by output time stamps. In each of theses stages the corresponding time stamp information linked with current frame data to be processed is regarded in order to control the overall delay of the processing.
In order to allow switchable bit rates for the video and audio encoders on operators choice, for example for making space for an additional TV channel, a switchable delay of the audio encoder is desireable. However, the European patent application 99250009 does not disclose, how such delay changes might be handled.